This invention relates generally to digital computer memory cells and particularly to apparatus and methods for supplying standby current to a static bipolar random access memory. Still more particularly, this invention relates to apparatus and methods for supplying standby current to a bipolar static random access memory cell to maintain a stored logic state.
A static semiconductor memory cell has the ability to store data indefinitely as long as sufficient power, known as the "standby power" is applied to the cell. In contrast, a dynamic memory requires that the stored data be periodically rewritten to prevent the data from becoming lost. Static memory cells are essentially flip flops that can maintain a given state indefinitely whereas dynamic memory cells use capacitances that must be periodically recharged.
In most prior static RAMs, the memory cell standby current flows from the most positive power supply to the most negative power supply and has no useful function other than providing the power required to maintain a stored logic state. An improved static RAM uses the standby current from a first group of memory cells to supply the power for a second group of memory cells.
The memory speed of a static RAM is a function of the standby power applied such that greater standby power results in a faster memory. Sophisticated digital computers require very fast memories. Accordingly, there is a need in the art for a bipolar static ECL RAM cell which better utilizes the available power to provide a memory speed superior to that of prior devices. Further, there is a need for greater efficiency in the use of standby power in integrated systems.